Our borad objective is to improve the quality of low vision care. The clinician attempting to help the low vision patient needs to have clinical tests that can predict the patient's disability at funcitonal tasks. In this project, a battery of clinical tests and a series of tests of functional vision will be assembled. These tests will be applied to 2 groups of subjects who show substantive changes in functional ability with changes in illumination. One group will have macular degeneration, the other retinitis pigmentosa. An added normal, age-matched control group will also be used. Controlling illumination will provide changes in the subjects' funcitonal disabilities. The clinical test scores associated with particular levels of disability will be determined for each subject. The strength of the association between test scores and disability levels will provide the predictive power of the clinical tests. The functional tasks to be tested are reading, face recognition, and mobility. The clinical tests considered are of (a) Visual Acuity: grating, single letters, letter charts, work reading, and low contrast letter charts; (b) Contrast Sensitivity: CSF's small and large field, edge detection, Arden gratings (with suitable controls), vistech VCTS and Bailey's contrast test; (c) Visual Fields: Dicon perimetry, Freidman field analyzer, Amsler Grid, and Reversed Contrast tangent screen; (d) Color Vision: with standard, desaturated, and large area Panel D-15 tests; and (e) as appropriate, there will be added testing to better define the extent and nature of the visual loss in cooperation with Professor Enoch's laboratory. Correlations and multiple correlations between clinical test scores and funcitonal abilities will be evaluated. Recommendations will be made advising clinicians which tests are most appropriate for predicting capabilities at the different functional tasks.